The present invention relates generally to an occupant restraint system of the type having a confinement which is expanded by a fluid supply to restrain movement of an occupant of a vehicle during a collision. Such an apparatus is illustrated and described in U.S. Pat. Nos. 3,516,685 and 3,602,572.
The expandable confinement has a collapsed inoperative condition for storage. Expansion of the confinement is generally effected by a fluid supply in the form of a single chamber of stored pressurized gas. Although the stored gas arrangement has proven to be satisfactory in performance and simplicity, the arrangement results in a relatively large, heavy-walled, high pressure vessel. A reduction in the size of the vessel and the storage pressure of the gas would be very beneficial.
To overcome the size and pressure difficulties, it has been suggested that a pyrotechnic, gas generation device be used as a fluid supply for inflating an occupant restraint cushion. Such a concept, however, has the disadvantage that gases, such as CO, NH.sub.3, NO.sub.2, HCN, SO.sub.2, H.sub.2, H.sub.2 S and CO.sub.2, might be produced in sufficient quantities as to exceed desirable toxicity limits for humans in the confinement and vehicle. Further, the gas generated by a pyrotechnic type material is at a sufficiently high temperature to increase the surface temperature of the inflated confinement above a tolerable limit. Besides the toxicity and temperature problems, expansion of the confinement, in order to adequately protect the occupants of the vehicle, should be initiated within milliseconds from the time a sensed collision condition is relayed to the fluid supply. Therefore, gas must be directed into the confinement and the toxicity and temperature problems must be solved in a minute period of time in order for the fluid suply to be an effective and useful source of gas for effecting expansion of the confinement.